plugins/wacom: Fix build without WAYLAND
The following Merge Request (MR) has been forwarded from GitHub in order to prevent the GNOME Project from losing contributions coming from un-official channels. And for contributors to not see their valuable contributions not being accounted for.
Relevant information:
Github handle: mtango
MR URL: https://github.com/GNOME/gnome-settings-daemon/pull/8
Patch URL: https://github.com/GNOME/gnome-settings-daemon/pull/8.patch
Body of the MR: